This invention relates to the manufacturing of polyester fabric for wipers, in particular, wipers which release fewer particulate contaminates.
Wipers may be made from knitted, woven or non-woven polyester fabrics. The typical manufacturing process begins with drawing and texturing continuous filament polyester yarn. The textured yarn is knitted or woven to construct a fabric, and the fabric is washed or scoured to remove spinning oils. The fabric may be chemically modified in order to improve its wettability and performance. The fabric is then dried in a "tenter frame" oven at a temperature of between 325 and 450.degree. F., to remove moisture and heat set the fabric. Heat setting dissipates stress in the polyester fibers and stabilizes the fabric.
Next, the fabric is cut into wipers, typically 9 inch by 9 inch squares. The wipers may remain unlaundered or may be washed in a cleanroom laundry, employing special surfactants and highly-filtered and purified water, to reduce the contamination present on the fabric. After washing, the wipers may be packaged dry in air-tight plastic bags, or pre-saturated with a suitable solvent before being packaged, and are ready for use.
These wipers are utilized for a number of different applications, including cleaning within cleanrooms, automotive painting rooms and other cleanroom environments. Each different application emphasizes certain standards these types of wipers should attain. For example, for wipers utilized in cleanrooms, stringent performance standards must be met. These standards are related to sorbency and contamination, including maximum allowable particulate, unspecified extractable matter and individual ionic contaminants. The standards for particulate contaminant release are especially rigorous and various methods have been devised to meet them. For example, Paley et al., U.S. Pat. No. 4,888,229, describes a wiper having fused borders, the sealed edge of the wipers being present to reduce contamination caused by small fibers. Diaber et al., U.S. Pat. No. 5,229,181, describes a knit fabric tube, only two edges of which must be cut and sealed, thereby reducing the contamination caused by loose fibers from the edges. Paley et al., U.S. Pat. No. 5,271,995, describes a wiper for a cleanroom environment that has reduced inorganic contaminants through the use of a specific yarn, namely "nylon bright". Reynolds, U.S. Pat. No. 5,069,735, describes a procedure to cut the fabric into pieces using a hot air jet in the range of 600 to 800.degree. F. to melt the fibers, forming a sealed edge product with reduced loose fiber contamination.
Despite advances made in reducing particulate contamination release from cleanroom wipers, further reductions in particulate release are, nevertheless, highly desirable.